Shotgun gauge adapter



Sept-5,1967 o. M. KNODE, JR, T L 3,339,304

SHOTGUN GAUGE ADAPTER Filed Oct. 23, 1965' 2 Sheets-Sheet 2 INVENTORS OLIVER M. KNOD JR. H DWARD M. 5742K United States Patent 3,339,304 SHOTGUN GAUGE ADAPTER Oliver M. Knode, Jr., Hampden, and Edward M. Stark,

East Longmeadow, Mass., assignor to Emhart Corporation, Bloomfield, Conn., a corporation of Connecticut Filed Oct. 23, 1965, Ser. No. 503,211 1 Claim. (Cl. 42-77) This invention relates to gun bore adapters, and more particularly to improved adapter tubes removably insertable in the gun to reduce the gun bore diameter, thus enabling the same gun to fire ammunition of gauge or caliber smaller than the barrel itself.

The principal object of this invention is to provide an improved gun-bore adapter, having particular utility in shotguns, of minimum weight capable of use with various types of shotguns without sacrifice of structural strength and safety in the critical breech pressure zone. For example, :by use of this adapter any standard 12 gauge shotgun can be adapted to fire a .410 gauge or other shell of less than 12 gauge by simply inserting a tube in the breech end of the barrel. When it is desired to fire 12 gauge shells, the tube can be readily removed. Moreover, the constructional characteristics of the tube are such that insertion and removal is accomplished without injury to the barrel.

The above and other objects and advantages of this invention will be more readily perceived from the following description with reference to the accompanying drawings, in which:

FIG. 1 is a partial perspective view showing an adapter tube embodying this invention being inserted into a shotgun barrel;

FIG. 2 is an elevational view partly in section showing an adapter tube disposed within the barrel of a gun;

FIGS. 3 and 4 are bottom partial views showing parts of the adapter in different operative relationships;

FIG. 5 is a perspective view of the adapter with a section broken away;

FIG. 6 is a sectional view generally taken along line 6-6 of FIG. 5;

FIG. 7 is an end view of the breech end of the adapter; and FIGS. 8 and 9 are enlarged perspective views showing separately elements of the adapter.

Referring now in detail to the drawings, a shotgun gauge adapter embodying this invention is shown generally at 6 in FIG. 1. The adapter is in the form of a tube removably insertable into the barrel 8 of any standard breakaction type of shotgun, shown generally at 10. The shotgun shown is a break-action type and includes an extractor 12 operated to extract expended shells from the barrel when the action is broken.

In accordance with this invention, the adapter 6 comprises a cartridge chamber or chamber member 14 with a barrel piece 16 extending from the front end of the chamber member 14. In the embodiment shown, the chamber member and barrel piece are each separately formed and joined together in any suitable manner, such as by screw threads provided on the mating ends of the two elements. The separate cartridge chamber 14- and the barrel piece 16 are each fabricated of a material best suited for the desired performance characteristics commensurate with their respective functions. Preferably to obtain maximum strength the cartridge chamber member 14 is made of suitable ferrous metal such as steel having the capability of withstanding peak explosive pressures during firing. The barrel, on the other hand, is preferably made of a lightweight non-ferrous material selected for machineability and strength, such as tempered aluminum, magnesium or the like.

Chamber member 14 of the adapter tube 6 is provided with a flange 18 disposed at one end, as shown in FIGS. 1, 5 and 7. The forward face of the flange is beveled, as shown at 20 in FIG. 2, to mate with the bevel 22 in the breech end of the gun barrel of any standard breakacti'on type shotgun. Thus when the tube is pushed fully into the gun barrel, the beveled flange centers the chamber member end of the tube within the barrel.

The flange 18 extends around only a portion of the tube leaving a circumferential notch or slot 24, as seen in FIGS. 1 and 7. The slot permits free back and forth movement of the shotgun extractor 12, and extends through a sufliciently large arc to accommodate the widest extractors found on standard model shotguns.

In addition to the flange or header 18, means for centering the adapter tube is also provided at the opposite or muzzle end of the adapter and comprises a flexible elastic ring 26, as shown in FIGS. 2 and 5. The ring is located adjacent the outer end of the barrel piece 16 and is fitted in an annular slot 28 provided in the barrel piece 16. The ring may be made of any suitably flexible, elastic material, such as various synthetic plastics, and including Teflon, neoprene, rubber and the like. The outer diameter of the ring is made sufliciently large to provide a snug fit in the gun barrel so that when the adapter is inserted into the barrel, the ring holds it centered and prevents the gun barrel being scratched by the metal tube. In addition, the ring 26 is made of a heat resistant material and is sufliciently tight to form a gas seal which prevents rearward escape of the gases. Moreover, the ring is readily removable and replaceable should it become worn or darnaged in any way.

The configuration of the cartridge chamber, forward of the flange or header 18', is in the form of two cylindrical portions 30 and 32 separated by a shoulder 33. (See FIGS. 1, 2, 3 and- 4.) It will be seen that the first cylindrical portion has a slightly smaller outer diameter than the barrel so as to provide clearance between the gun barrel and the adapter tube. Forward of the section 32, the cartridge member is provided with a circumferentially extending recess or slot 34 into which is fitted a clip or ring 36 which serves as a stroke limiting and retaining means for an extractor member 38 slidably mounted in longitudinally extending recess 40 provided in the cartridge chamber 14 (FIGS. 2 and 5). 1

7 Forward of the slot 34, the adapter tube continues as a cylindrical section for a suflicient distance to provide the chamber at least as long as a shotgun shell, shown at 42 in FIG. 2. The cartridge chamber 14 then tapers inwardly as shown at 45, and terminates in a threaded extension 44 which screws into a correspondingly threaded bore of the barrel piece 16 of the adapter (FIG. 5). The two sections may be permanently locked or bonded in place by the addition to the threaded portion 44 of a small amount of resin adhesive or other suitable material.

From the threaded coupling, the barrel piece tapers inwardly to a cylindrical portion over the major portion of its length, as shown at 48 in FIGS. 2 and 5. At its outer end, the tubes outer diameter increases again to provide sufficient thickness of metal for flaring of the inner bore and for the ring-retaining slot 28, and to provide suflicient diameter so that the elastic ring fits snugly into the barrel of the shotgun with which it is intend to be used. The flare or taper of the inner bore at the terminal end thereof, as shown at 50 in FIG. 2, prevents appreciable buildup of burned powder residue beyond the muzzle end of the tube.

The extractor bar 38, comprises a metal bar, slidably mounted in an undercut open ended longitudinally extending recess 40. In the preferred embodiment of the invention, as seen most clearly in FIGS. 6 and 7, the undercut recess 40 is of dovetail configuration. In FIG. 9, it will be noted that one end of the extractor member is provided with radially extending lugs 52 and 54 respectively. The extractor member is further characterized by a neck portion 56 of reduced width which provides oppositely disposed longitudinally extending notches 58 and 60. As will be described below, these notches cooperate with the spring metal clip 36 to provide adjustable stop means for varying the stroke of the extractor bar.

The clip 36 (FIGS. 5 and 8) is generally a split ring construction which enables the clip to be flexed for installation and removal from the slot 34. The free ends of the clip are notched to provide circumferentially extending oppositely disposed projections or tabs 64. These tabs extend inwardly of the side edges of recess 40 so as tointerengagethe extractor member 38 in its outermost position, as shown in FIGS. 3 and 4 of the drawings. Thus, the tabs serve as a stop and retaining means for the extractor bar 38.

When the shotgun barrel is opened and the extractor 12 (FIG. 1) moves rearwardly, the gun extractor 12 engages the inwardly extending lug 54 of the extractor bar 38 carrying the bar rearwardly until the front, inner shoulders of notches 58 and 60 come into contact with the projections 64 of the clip 36 (FIGS. 1 and 2). As clearly shown in FIG. 2, the outwardly extending lug 52 of the extractor member 38 engages the rim of the shotgun shell 42 and extracts it from the chamber member 14 of the adapter tube. When a round is loaded and the action closed, the face 70 (FIG. 1) of the shotgun breech engages in succession, the extractor 12, the extractor bar 38, and the shotbun shell 42 moving them forwardly.

As shown in FIG. 4, the clip 36 may be positioned with its stop tabs or projections 64 disposed toward the chamber member end of the adapter tube for shotguns having a long extractor stroke. The clip may be reversed simply by snapping it ofi the tube and refitting it thereon with the stop tab 64 disposed toward the muzzle end of the adapter, as shown in FIG. 3. In this position of the clip 36, the adapter may be used with shotguns having a short extractor stroke. In both positions, the projections cooperate with the notches in the bar 38 to serve as stop means when contacted by inner edges of the notches. The reversible feature assures that the extractor stroke of the bar 38 will be generally the same length as long or short extractor strokes of standard types of shotguns. To achieve this purpose, the dimension a (FIG. 8) of the clip 36 is made equal to the difference in length between the long and short extractor strokes of standard break-action type shotguns.

To use the adapter embodying this invention, it is preferable to lightly oil the resilent ring 26 at the muzzle end of the adapter. Then with the clip 36 disposed in accordance with the length of the extractor stroke of the particular gun, the adapter is simply pushed into the breech end of the shotgun barrel 8 as though it were a shotgun shell. In doing this the extractor bar 38 is registered or centered on the extractor 12 of the gun. The adapter is pushed all the way into the barrel so that it is fiush with the breech end thereof. The gun can now be loaded and operated, using a smaller gauge shell in exactly the same manner as in using larger gauge ammunition.

By providing a cartridge member of steel and lightweight barrel piece, such as aluminum, it is possible to achieve weight reduction of as much as fifty percent, as compared with an integral all steel adapter tube. Moreover, this drastic weight reduction, most important in hand carried firearms, is obtained without sacrifice in structural strength and safety, since the adapter with its steel chamber member is structurally capable of withstanding peak explosive pressures and is fabricated with sufiicient wall strength whereby the extractor slide and retaining ring recesses may be cut in the adapter wall without reducing the wall strength below normal safety limits.

Having thus described this invention, what is claimed Adapter to reduce a gun bore diameter comprising a composite tubular structure having a steel chamber member and a lightweight non-ferrous metal barrel piece affixed to the end of the chamber member, said chamber member being formed with a longitudinally extending undercut recess, an extractor bar slidably mounted in said recess, an elastic ring carried adjacent the terminal end of said barrel piece, and a metal clip in the form of a split ring disposed on said chamber member, the free ends of said ring terminating in spaced opposed relationship, a projection extending into the split formed by the free ends of said ring, said projection being axially offset from the circumferential center line of said ring so that end-to-end Iraeversal of the clip changes the stroke of said extractor References Cited UNITED STATES PATENTS BENJAMIN A. BORCHELT, Primary Examiner. 

